Sunday, 27 March 2016

Eruptions from new vent on Mount Nyiragongo, Democratic Republic of Congo.

The Observatoire Volcanologique de Goma has raised concerns about the possibility of a major eruptive episode on Mount Nyiragongo in the Virungu Mountiains of the North Kivu Province in eastern Democratic Republic of Congo. Local people in the area began to report loud and continuous rumblings from the volcano early in February 2016, and an expedition to the volcano by staff at the observatory at the beginning of March found that a new vent had opened at the northeastern end of the lower crater terrace, with lava issuing from this and forming a second lava lake (such a lake has been present at the volcano's main vent since 2002). A second visit to the volcano on 10-11 March found that lava had begun to flow from the new lake into the original one, though overall activity did seem to have subsided slightly.

The new lava lake on Mount Nyiragongo on 11 March 2016. Note lava flowing from the lake on the right side of the image. Observatoire Volcanologique de Goma.

This vent is considered to be particularly dangerous as it lies on one of two major fracture zones which run through the volcano. Eruptions on these fracture zones can cause the main edifice of the volcano to split, allowing lava that has built up in lakes within the central caldera over years or decades to drain rapidly, leading to rapidly flowing lava flows that spread over the surrounding countryside. The most recent two such episodes, in 1977 and 2002, both killed over a thousand people each, with a lava flow from the 2002 eruption destroying a large part of the town of Goma.

The new lava lake on 28 February 2016.

Nyiragongo and neighbouring volcano Nyamuragira account for 40% of all volcanic activity on
the African continent. They produce a low silicone basalt. This tends to
have a very low viscosity, i.e. it flows very freely, rapidly covering a
wide area. Because of this few people choose to live near the
mountains, so they are seldom a threat to human life, though it has in
the past caused problems for vulnerable wildlife populations, such as
the human-familiarised chimpanzees and gorillas of Virungu National Park.

Nyamuragira and Nyiragongo lie on the Eastern Branch of the East African
Rift; most volcanoes in this area produce more typical siliclastic
lavas, but there are several other basaltic volcanoes in the area, such
as the less active Visoke, which last erupted in 1957, and the inactive
Karasimbi, Mikeno and Muhavura volcanoes. The Western Branch of the Rift
Valley also has basaltic volcanoes, most notably Ol Doinyo Lengi, to
the south of Lake Natron in Tazania, the worlds only active carbonitic
volcano (i.e a volcano that produces lavas containing carbonate
compounds), and the nearby extinct, but dramatic, Mount Shombole.

The locations of Nyamuragira (purple) and Nyiragongo (red). Google Maps.

The East African Rift is slowly splitting the African Plate in two along
a line from the Red Sea through Ethiopia, and which includes the great
lakes and volcanoes of east-central Africa. This has the potential to
open into a new ocean over the next few tens of millions of years,
splitting Africa into two new, smaller, continents; Nubia to the west
and Somalia to the east.

Eruptions from Nyamuragira and Nyiragongo also tend to be unusually rich
in Sulphur Dioxide (SO₂), with the volcano producing a large proportion
of all the volcanic SO₂ that enters our atmosphere. To give this a
sense of proportion, about 75% of all the SO₂ entering our atmosphere
originates from the burning of fossil fuels. The effects of SO₂ in the
atmosphere are a little complicated. Firstly it is poisonous, though
this is only a danger close to the source where it is concentrated.
Since most people avoid going close to active volcanoes, this usually
only presents a hazard to professional volcanologists. Secondly it mixes
with water to form sulphuric acid, i.e. acid rain, which can be a major
problem downwind of volcanic eruptions and large industrial centres,
with the rain causing severe damage to vegetation and aquatic life.
Thirdly SO₂ droplets act as coolant. Since both volcanic and industrial
SO₂ is usually produced alongside larger quantities of Carbon Dioxide
(CO₂), which is a greenhouse gas, this is usually a negligible effect,
but cooler weather can be produced downwind of major eruptions, as the
CO₂ disperses more rapidly than the SO₂.

Seismic activity on Mount Nyamulagira, Democratic Republic of Congo.The Volcanic Observatory of Goma have issued a warning of a possible
impending eruption on Mount Nyamulagira, an active volcano close to
Mount Nyiragongo in the Virungu Mountains of eastern Democratic Republic
of Congo, about 25 km to the north of Lake Kivu. Mount Nyamalugira is...

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About Me

Studied Palaeobiology & Evolution at the University of Portsmouth, Geosciences via the Open University & Ecology and Conservation at Christchurch University, Canterbury.
Have worked in wildlife based tourism, mineral exploration, development, conservation, education & environmental chemistry. Occasionally write articles for papers and magazines.

This Blog would be impossible without the work of countless scientists (and others) throughout the world. Where possible I do my best to credit them, but there will always be many more who remain unmentioned; this does not imply I am ungrateful for their contributions. Any errors or inaccuracies are, of course, my own.